Agricultural implements often include tools or row units that must be aligned relative to a row of crop or tillage or seeding area in a field. For example, currently available cotton harvesters include row units supported from a lift frame and transversely adjustable on the frame to change row spacings. If a skip row pattern of planting is employed, the units may have to be repositioned to line up with the rows. Examples of transversely adjustable a row units are shown in commonly assigned U.S. Pat. Nos. 4,803,830; 4,896,492 and 6,079,192.
In many of the adjustable arrangements, a friction interface propels the units in a specified direction. If the friction surfaces are wet or if the unit is under a heavy side load, friction between the roller and a support rail on the frame may be insufficient to transfer the rotary motion into a force significant enough to move the units in the desired direction. The driving sheave will simply spin and the unit will not move.
Other harvester row unit designs include use of a hydraulic cylinder or similar arrangement to move the row units laterally to follow the planted rows in the field. An example of hydraulic cylinder controlled transverse adjustment is shown in the aforementioned U.S. Pat. No. 6,079,192. Such designs typically are very large and present space constraint problems. In addition, alternate brackets and cylinder positions must be utilized for varying row spacings and for unit cleaning operations.